NIST Special Publication 800-150

Guide to Cyber Threat
Information Sharing
Chris Johnson
Lee Badger
David Waltermire
Julie Snyder
Clem Skorupka

This publication is available free of charge from:http://dx.doi.org/10.6028/NIST.SP.800-150

C O M P U T E R

S E C U R I T Y

NIST Special Publication 800-150

Guide to Cyber Threat
Information Sharing
Chris Johnson
Lee Badger
David Waltermire
Computer Security Division
Information Technology Laboratory
Julie Snyder
Clem Skorupka
The MITRE Corporation

This publication is available free of charge from:http://dx.doi.org/10.6028/NIST.SP.800-150

October 2016

U.S. Department of Commerce
Penny Pritzker, Secretary
National Institute of Standards and Technology
Willie May, Under Secretary of Commerce for Standards and Technology and Director

Authority
This publication has been developed by NIST in accordance with its statutory responsibilities under theFederal Information Security Modernization Act (FISMA) of 2014, 44 U.S.C. § 3551 et seq., Public Law(P.L.) 113-283. NIST is responsible for developing information security standards and guidelines, including
minimum requirements for federal information systems, but such standards and guidelines shall not apply
to national security systems without the express approval of appropriate federal officials exercising policy
authority over such systems. This guideline is consistent with the requirements of the Office of Management
and Budget (OMB) Circular A-130.
Nothing in this publication should be taken to contradict the standards and guidelines made mandatory andbinding on federal agencies by the Secretary of Commerce under statutory authority. Nor should theseguidelines be interpreted as altering or superseding the existing authorities of the Secretary of Commerce,
Director of the OMB, or any other federal official. This publication may be used by nongovernmentalorganizations on a voluntary basis and is not subject to copyright in the United States. Attribution would,
however, be appreciated by NIST.
National Institute of Standards and Technology Special Publication 800-150
Natl. Inst. Stand. Technol. Spec. Publ. 800-150, 35 pages (October 2016)
CODEN: NSPUE2This publication is available free of charge from:http://dx.doi.org/10.6028/NIST.SP.800-150
Certain commercial entities, equipment, or materials may be identified in this document in order to describe an
experimental procedure or concept adequately. Such identification is not intended to imply recommendation or
endorsement by NIST, nor is it intended to imply that the entities, materials, or equipment are necessarily the best
available for the purpose.
There may be references in this publication to other publications currently under development by NIST in accordancewith its assigned statutory responsibilities. The information in this publication, including concepts and methodologies,
may be used by federal agencies even before the completion of such companion publications. Thus, until eachpublication is completed, current requirements, guidelines, and procedures, where they exist, remain operative. For
planning and transition purposes, federal agencies may wish to closely follow the development of these new
publications by NIST.
Organizations are encouraged to review all draft publications during public comment periods and provide feedback to
NIST. Many NIST cybersecurity publications, other than the ones noted above, are available at
http://csrc.nist.gov/publications.

Comments on this publication may be submitted to:
National Institute of Standards and Technology
Attn: Computer Security Division, Information Technology Laboratory
100 Bureau Drive (Mail Stop 8930) Gaithersburg, MD 20899-8930
Email: sp800-150comments@nist.gov

All comments are subject to release under the Freedom of Information Act (FOIA).

iNIST SP 800-150

GUIDE TO CYBER THREAT INFORMATION SHARING

Reports on Computer Systems Technology
The Information Technology Laboratory (ITL) at the National Institute of Standards and Technology(NIST) promotes the U.S. economy and public welfare by providing technical leadership for the Nation’s
measurement and standards infrastructure. ITL develops tests, test methods, reference data, proof of concept
implementations, and technical analyses to advance the development and productive use of information
technology. ITL’s responsibilities include the development of management, administrative, technical, andphysical standards and guidelines for the cost-effective security and privacy of other than national securityrelated information in federal information systems. The Special Publication 800-series reports on ITL’s
research, guidelines, and outreach efforts in information system security, and its collaborative activities
with industry, government, and academic organizations.
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Abstract
Cyber threat information is any information that can help an organization identify, assess, monitor, andrespond to cyber threats. Cyber threat information includes indicators of compromise; tactics, techniques,and procedures used by threat actors; suggested actions to detect, contain, or prevent attacks; and thefindings from the analyses of incidents. Organizations that share cyber threat information can improvetheir own security postures as well as those of other organizations.
This publication provides guidelines for establishing and participating in cyber threat information sharing
relationships. This guidance helps organizations establish information sharing goals, identify cyber threat
information sources, scope information sharing activities, develop rules that control the publication anddistribution of threat information, engage with existing sharing communities, and make effective use of
threat information in support of the organization’s overall cybersecurity practices.

Keywords
cyber threat; cyber threat information sharing; indicators; information security; information sharing

Acknowledgments
The authors, Chris Johnson, Lee Badger, and David Waltermire of the National Institute of Standards andTechnology (NIST), and Julie Snyder and Clem Skorupka of The MITRE Corporation, wish to thanktheir colleagues who contributed to this publication, including Tom Millar and Rich Struse of the
Department of Homeland Security (DHS); Karen Quigg, Richard Murad, Carlos Blazquez, and Jon Baker
of The MITRE Corporation; Murugiah Souppaya and Melanie Cook of NIST; Ryan Meeuf, of the
Software Engineering Institute, Carnegie Mellon University; George Saylor, Greg Witte, and Matt Smithof G2 Inc.; Karen Scarfone of Scarfone Cybersecurity; Chris Bean of the National Security Agency(NSA); Eric Burger of the Georgetown Center for Secure Communications, Georgetown University; Joe
Drissel of Cyber Engineering Services Inc.; Tony Sager of the Center for Internet Security; Kent
Landfield of Intel Security; Bruce Potter of KEYW Inc.; Jeff Carpenter of Dell SecureWorks; Ben Millerof the North American Electric Reliability Corporation (NERC); Anton Chuvakin of Gartner, Inc.;
Johannes Ullrich of the SANS Technology Institute; Patrick Dempsey, Defense Industrial Base
Collaborative Information Sharing Environment (DCISE); Matthew Schuster, Mass Insight; Garrett
Schubert of EMC; James Caulfield of the Federal Reserve; Bob Guay of Biogen; and Chris Sullivan of
Courion.

Trademark Information
All registered trademarks or trademarks belong to their respective organizations.

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Executive Summary
Cyber attacks have increased in frequency and sophistication, presenting significant challenges fororganizations that must defend their data and systems from capable threat actors. These actors range fromindividual, autonomous attackers to well-resourced groups operating in a coordinated manner as part of acriminal enterprise or on behalf of a nation-state. Threat actors can be persistent, motivated, and agile, andthey use a variety of tactics, techniques, and procedures (TTPs) to compromise systems, disrupt services,commit financial fraud, and expose or steal intellectual property and other sensitive information. Given
the risks these threats present, it is increasingly important that organizations share cyber threat
information and use it to improve their security posture.
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Cyber threat information is any information that can help an organization identify, assess, monitor, andrespond to cyber threats. Examples of cyber threat information include indicators (system artifacts orobservables associated with an attack), TTPs, security alerts, threat intelligence reports, andrecommended security tool configurations. Most organizations already produce multiple types of cyberthreat information that are available to share internally as part of their information technology andsecurity operations efforts.
By exchanging cyber threat information within a sharing community, organizations can leverage thecollective knowledge, experience, and capabilities of that sharing community to gain a more complete
understanding of the threats the organization may face. Using this knowledge, an organization can makethreat-informed decisions regarding defensive capabilities, threat detection techniques, and mitigation
strategies. By correlating and analyzing cyber threat information from multiple sources, an organization
can also enrich existing information and make it more actionable. This enrichment may be achieved byindependently confirming the observations of other community members, and by improving the overall
quality of the threat information through the reduction of ambiguity and errors. Organizations that receive
threat information and subsequently use this information to remediate a threat confer a degree ofprotection to other organizations by impeding the threat’s ability to spread. Additionally, sharing of cyberthreat information allows organizations to better detect campaigns that target particular industry sectors,
business entities, or institutions.
This publication assists organizations in establishing and participating in cyber threat information sharing
relationships. The publication describes the benefits and challenges of sharing, clarifies the importance oftrust, and introduces specific data handling considerations. The goal of the publication is to provide
guidelines that improve cybersecurity operations and risk management activities through safe andeffective information sharing practices, and that help organizations plan, implement, and maintain
information sharing.
NIST encourages greater sharing of cyber threat information among organizations, both in acquiring
threat information from other organizations and in providing internally-generated threat information toother organizations. Implementing the following recommendations enables organizations to make more
efficient and effective use of information sharing capabilities.
Establish information sharing goals and objectives that support business processes and security
policies.
An organization’s information sharing goals and objectives should advance its overall cybersecurity
strategy and help an organization more effectively manage cyber-related risk. An organization should use
the combined knowledge and experience of its own personnel and others, such as members of cyber threat
information sharing organizations, to share threat information while operating per its security, privacy,
regulatory, and legal compliance requirements.

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Identify existing internal sources of cyber threat information.
Organizations should identify tools, sensors, and repositories that collect, produce, or store cyber threat
information, threat analytics platforms, and delivery mechanisms that support the exchange of cyberthreat information. As internal cyber threat information sources and capabilities are identified,organizations should determine how information from these sources currently support cybersecurity andrisk management activities. Organizations should also document observed knowledge gaps and consider
acquiring additional threat information from other (possibly external) sources or through the deploymentof other tools or sensors. Finally, organizations should identify threat information that is available andsuitable for sharing with outside parties.
Specify the scope of information sharing activities.
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

The breadth of an organization’s information sharing activities should be consistent with its resources,abilities, and objectives. Information sharing efforts should focus on activities that provide the greatest
value to an organization and its sharing partners. The scoping activity should identify types of informationthat an organization’s key stakeholders authorize for sharing, the circumstances under which sharing of
this information is permitted, and those with whom the information can and should be shared.
Establish information sharing rules.
Sharing rules are intended to control the publication and distribution of threat information, andconsequently help to prevent the dissemination of information that, if improperly disclosed, may haveadverse consequences for an organization, its customers, or its business partners. Information sharing
rules should take into consideration the trustworthiness of the recipient, the sensitivity of the shared
information, and the potential impact of sharing (or not sharing) specific types of information.
Join and participate in information sharing efforts.
An organization should identify and participate in sharing activities that complement its existing threat
information capabilities. An organization may need to participate in multiple information sharing forums
to meet its operational needs. Organizations should consider public and private sharing communities,
government repositories, commercial cyber threat information feeds, and open sources such as public
websites, blogs, and data feeds.
Actively seek to enrich indicators by providing additional context, corrections, or suggested
improvements.
When possible, organizations should increase the usefulness and effectiveness of threat information by
producing metadata for each indicator that is generated. Such metadata can provide context regarding theindicator by describing the intended use of the indicator, how it is to be interpreted, and how it relates toother indicators. Additionally, sharing processes should include mechanisms for publishing indicators,
updating indicators and associated metadata, and retracting submissions that are incorrect or perhaps
inadvertently shared. Such feedback plays an important role in the enrichment, maturation, and quality of
the indicators shared within a community.
Use secure, automated workflows to publish, consume, analyze, and act upon cyber threat
information.
The use of standardized data formats and transport protocols to share cyber threat information makes it
easier to automate threat information processing. The use of automation enables cyber threat information

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to be rapidly shared, transformed, enriched, analyzed, and acted upon with less need for manualintervention.
Proactively establish cyber threat sharing agreements.
Rather than attempting to establish sharing agreements during an active cyber incident, organizations
should plan ahead and have agreements in place before incidents occur. Such advanced planning helps
ensure that participating organizations establish trusted relationships and understand their roles,
responsibilities, and information handling requirements.
Protect the security and privacy of sensitive information.
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Sensitive information such as controlled unclassified information (CUI) [16] and personally identifiable
information (PII) may be encountered when handling cyber threat information. The improper disclosureof such information could cause financial loss; violate laws, regulations, and contracts; be cause for legal
action; or damage an organization’s or individual’s reputation. Accordingly, organizations should
implement the necessary security and privacy controls and handling procedures to protect this informationfrom unauthorized disclosure or modification.
Provide ongoing support for information sharing activities.
Each organization should establish an information sharing plan that provides for ongoing infrastructure
maintenance and user support. The plan should address the collection and analysis of threat informationfrom both internal and external sources and the use of this information in the development anddeployment of protective measures. A sustainable approach is necessary to ensure that resources areavailable for the ongoing collection, storage, analysis, and dissemination of cyber threat information.

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Table of Contents
Executive Summary .................................................................................................................iii
1.

Introduction ....................................................................................................................... 1
1.1
1.2
1.3

2.

Basics of Cyber Threat Information Sharing ................................................................... 2

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2.1
2.2
2.3
3.

Threat Information Types...........................................................................................2
Benefits of Information Sharing..................................................................................3
Challenges to Information Sharing .............................................................................4

Establishing Sharing Relationships................................................................................. 6
3.1
3.2
3.3
3.4

3.5
3.6
4.

Purpose and Scope ...................................................................................................1
Audience ...................................................................................................................1
Document Structure...................................................................................................1

Define Information Sharing Goals and Objectives .....................................................6
Identify Internal Sources of Cyber Threat Information ................................................6
Define the Scope of Information Sharing Activities ....................................................9
Establish Information Sharing Rules ..........................................................................93.4.1 Information Sensitivity and Privacy ...............................................................11
3.4.2 Sharing Designations ...................................................................................143.4.3 Cyber Threat Information Sharing and Tracking Procedures ........................16
Join a Sharing Community.......................................................................................16
Plan to Provide Ongoing Support for Information Sharing Activities ......................... 18

Participating in Sharing Relationships ...........................................................................20
4.1
4.2
4.3
4.4
4.5

Engage in Ongoing Communication ........................................................................20
Consume and Respond to Security Alerts ...............................................................21
Consume and Use Indicators ..................................................................................21
Organize and Store Cyber Threat Information .........................................................23
Produce and Publish Indicators ...............................................................................25
4.5.1 Indicator Enrichment ....................................................................................25
4.5.2 Standard Data Formats ................................................................................25
4.5.3 Protection of Sensitive Data .........................................................................26

List of Appendices
Appendix A— Cyber Threat Information Sharing Scenarios ...............................................27
Appendix B— Glossary ..........................................................................................................30
Appendix C— Acronyms ........................................................................................................32
Appendix D— References ......................................................................................................34

List of Tables
Table 3-1: Selected Internal Information Sources...................................................................... 7
Table 3-2: Handling Recommendations for Selected Types of Sensitive Data .........................12
Table 3-3: Traffic Light Protocol, Version 1.0 ...........................................................................15vi

NIST SP 800-150

1.

Introduction

1.1

Purpose and Scope

GUIDE TO CYBER THREAT INFORMATION SHARINGThis publication provides guidance to help organizations exchange cyber threat information. The
guidance addresses sharing of cyber threat information within an organization, consuming and using
cyber threat information received from external sources, and producing cyber threat information that canbe shared with other organizations. The document also presents specific considerations for participation in
information sharing communities.

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

This publication expands upon the information sharing concepts introduced in Section 4, Coordination
and Information Sharing, of NIST Special Publication (SP) 800-61[1].
1.2

Audience

This publication is intended for computer security incident response teams (CSIRTs), system and network
administrators, cybersecurity specialists, privacy officers, technical support staff, chief information
security officers (CISOs), chief information officers (CIOs), computer security program managers, andothers who are key stakeholders in cyber threat information sharing activities.
Although this guidance is written primarily for federal agencies, it is intended to be applicable to a wide
variety of governmental and non-governmental organizations.
1.3

Document Structure

The remainder of this document is organized into the following sections and appendices:•

Section 2 introduces basic cyber threat information sharing concepts, describes the benefits of sharing
information, and discusses the challenges faced by organizations as they implement sharing
capabilities.

•

Section 3 provides guidelines on establishing sharing relationships with other organizations.

•

Section 4 discusses considerations for effectively participating in sharing relationships.

•

Appendix A contains scenarios that show how organizations can enhance their network defenses by
sharing cyber threat information and by leveraging the cyber experience and capabilities of theirpartners.

•

Appendix B contains a list of terms used in the document and their associated definitions.

•

Appendix C provides a list of acronyms used in the document.

•

Appendix D identifies resources referenced in the document.

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Basics of Cyber Threat Information Sharing

This section introduces basic cyber threat information sharing concepts including types of cyber threat
information and common terminology. The section also examines potential uses for shared cyber threat
information and explores the benefits and challenges of threat information sharing.
2.1

Threat Information Types

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

A cyber threat is “any circumstance or event with the potential to adversely impact organizational
operations (including mission, functions, image, or reputation), organizational assets, individuals, otherorganizations, or the Nation through an information system via unauthorized access, destruction,
disclosure, or modification of information, and/or denial of service.” [2] For brevity, this publication uses
the term threat instead of “cyber threat”. The individuals and groups posing threats are known as “threat
actors” or simply actors.
Threat information is any information related to a threat that might help an organization protect itself
against a threat or detect the activities of an actor. Major types of threat information include thefollowing:•

Indicators are technical artifacts or observables 1 that suggest an attack is imminent or is currently
underway or that a compromise may have already occurred. Indicators can be used to detect anddefend against potential threats. Examples of indicators include the Internet Protocol (IP) address of asuspected command and control server, a suspicious Domain Name System (DNS) domain name, a
Uniform Resource Locator (URL) that references malicious content, a file hash for a malicious
executable, or the subject line text of a malicious email message.

•

Tactics, techniques, and procedures (TTPs) describe the behavior of an actor. Tactics are high-leveldescriptions of behavior, techniques are detailed descriptions of behavior in the context of a tactic,
and procedures are even lower-level, highly detailed descriptions in the context of a technique. TTPs
could describe an actor’s tendency to use a specific malware variant, order of operations, attack tool,
delivery mechanism (e.g., phishing or watering hole attack), or exploit.

•

Security alerts, also known as advisories, bulletins, and vulnerability notes, are brief, usually humanreadable, technical notifications regarding current vulnerabilities, exploits, and other security issues.
Security alerts originate from sources such as the United States Computer Emergency Readiness
Team (US-CERT), Information Sharing and Analysis Centers (ISACs), the National Vulnerability
Database (NVD), Product Security Incident Response Teams (PSIRTs), commercial security service
providers, and security researchers.

•

Threat intelligence reports are generally prose documents that describe TTPs, actors, types ofsystems and information being targeted, and other threat-related information that provides greater
situational awareness to an organization. Threat intelligence is threat information that has been
aggregated, transformed, analyzed, interpreted, or enriched to provide the necessary context for
decision-making processes.

•

Tool configurations are recommendations for setting up and using tools (mechanisms) that support
the automated collection, exchange, processing, analysis, and use of threat information. For example,
tool configuration information could consist of instructions on how to install and use a rootkit

1 An observable is an event (benign or malicious) on a network or system.

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detection and removal utility, or how to create and customize intrusion detection signatures, router
access control lists (ACLs), firewall rules, or web filter configuration files.
Many organizations already produce and share threat information internally. For example, anorganization’s security team may identify malicious files on a compromised system when responding toan incident and produce an associated set of indicators (e.g., file names, sizes, hash values). These
indicators might then be shared with system administrators who configure security tools, such as hostbased intrusion detection systems, to detect the presence of these indicators on other systems. Likewise,
the security team may launch an email security awareness initiative in response to an observed rise inphishing attacks within the organization. These practices demonstrate information sharing within an
organization.
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

The primary goal of this publication is to foster similar threat information sharing practices acrossorganizational boundaries – both acquiring threat information from other organizations, and providing
internally-generated threat information to other organizations.
2.2

Benefits of Information Sharing

Threat information sharing provides access to threat information that might otherwise be unavailable to anorganization. Using shared resources, organizations can enhance their security posture by leveraging theknowledge, experience, and capabilities of their partners in a proactive way. Allowing “oneorganization’s detection to become another’s prevention” 2 is a powerful paradigm that can advance theoverall security of organizations that actively share threat information.
An organization can use shared threat information in many ways. Some uses are operationally oriented,
such as updating enterprise security controls for continuous monitoring with new indicators andconfigurations to detect the latest attacks and compromises. Threat information may also be usedstrategically, such as using shared threat information as inputs when planning major changes to anorganization’s security architecture.
Threat information exchanged within communities organized around specific industries or sectors (orsome other shared characteristic) can be particularly beneficial because the member organizations often
face actors that use common TTPs that target the same types of systems and information. Cyber defense ismost effective when organizations work together to deter and defend against well-organized, capable
actors. Such collaboration helps to reduce risk and improve the organization’s security posture.
Benefits of information sharing include:•

Shared Situational Awareness. Information sharing enables organizations to leverage the collective
knowledge, experience, and analytic capabilities of their sharing partners within a community ofinterest, thereby enhancing the defensive capabilities of multiple organizations. Even a single
contribution—a new indicator or observation about an actor—can increase the awareness and securityof an entire community.

•

Improved Security Posture. By developing and sharing threat information, organizations gain abetter understanding of the threat environment and can use threat information to inform theircybersecurity and risk management practices. Using shared information, organizations can identify
affected platforms or systems, implement protective measures, enhance detection capabilities, andmore effectively respond and recover from incidents based on observed changes in the threat
environment. As organizations share information and subsequently mitigate threats, those

2 This phrase, which has been used in numerous presentations and discussions, was formulated by Tony Sager, Senior VP and
Chief Evangelist, Center for Internet Security.

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organizations can improve their overall cybersecurity posture, even providing a degree of protection
to other organizations, including those who may not have responded to the threat information, by
reducing the number of viable attack vectors for actors.

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150•

Knowledge Maturation. When seemingly unrelated observations are shared and analyzed byorganizations, those observations can be correlated with data collected by others. This enrichment
process increases the value of information by enhancing existing indicators and by developing
knowledge of actor TTPs that are associated with a specific incident, threat, or threat campaign.
Correlation can also impart valuable insights into the relationships that exist between indicators.

•

Greater Defensive Agility. Actors continually adapt their TTPs to try to evade detection, circumvent
security controls, and exploit new vulnerabilities. Organizations that share information are often
better informed about changing TTPs and the need to rapidly detect and respond to threats. Thisawareness helps increase their operational tempo and reduce the probability of successful attack. Suchagility also creates economies of scale for network defenders while increasing actors’ costs by forcing
them to develop new TTPs.

2.3

Challenges to Information Sharing

While sharing threat information clearly has benefits, certain challenges still remain. Some challenges
that apply both to consuming and to producing threat information are:•Establishing Trust. Trust relationships form the basis for information sharing, but require effort toestablish and maintain. Ongoing communication through regular in-person meetings, phone calls, or
social media can help accelerate the process of building trust.

•Achieving Interoperability and Automation. Standardized data formats and transport protocols areimportant building blocks for interoperability. The use of common formats and protocols enables
automation and allows organizations, repositories, and tools to exchange threat information atmachine speed. Adopting specific formats and protocols, however, can require significant time andresources, and the value of these investments can be substantially reduced if sharing partners requiredifferent formats or protocols. During the standards development process, early adopters need toaccept the risk that it may be necessary to purchase new tools if significant changes to formats andprotocols take place.

•

Safeguarding Sensitive Information. Disclosure of sensitive information, such as controlled
unclassified information (CUI) and personally identifiable information (PII) can result in financial
loss, violation of sharing agreements, legal action, and loss of reputation. Sharing security and event
information, such as security logs or scan results, could expose the protective or detective capabilitiesof the organization and result in threat shifting by the actor. 3 The unauthorized disclosure of
information may impede or disrupt an ongoing investigation, jeopardize information needed for future
legal proceedings, or disrupt response actions such as botnet takedown operations. Organizations
should apply handling designations to shared information and implement policies, procedures, andtechnical controls to actively manage the risks of disclosure of sensitive information.

3

NIST SP 800-30 Revision 1, Guide for Conducting Risk Assessments, defines threat shifting as “the response of adversaries toperceived safeguards and/or countermeasures (i.e., security controls), in which adversaries change some characteristic of theirintent/targeting in order to avoid and/or overcome those safeguards/countermeasures. Threat shifting can occur in one or moredomains including: (i) the time domain (e.g., a delay in an attack or illegal entry to conduct additional surveillance); (ii) the target
domain (e.g., selecting a different target that is not as well protected); (iii) the resource domain (e.g., adding resources to theattack in order to reduce uncertainty or overcome safeguards and/or countermeasures); or (iv) the attack planning/attack method
domain (e.g., changing the attack weapon or attack path).” [2, p.9]

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GUIDE TO CYBER THREAT INFORMATION SHARINGThis publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150•

Protecting Classified Information. Information received from government sources may be marked
as classified, making it difficult for an organization to use. Acquiring and maintaining the clearances
needed for ongoing access to classified information sources is expensive and time-consuming fororganizations. In addition, many organizations employ non-U.S. citizens who are not eligible to holdsecurity clearances and are not permitted access to classified information. [3]•Enabling Information Consumption and Publication. Organizations that want to consume andpublish threat information need to have the necessary infrastructure, tools, personnel, and training to
do so. Information sharing initiatives should be carefully scoped, because high-frequency, highvolume information exchanges have the potential to overwhelm an organization’s processing
capabilities. Organizations that are currently unable to support automated indicator exchange can
explore other options such as the manual exchange of best practices or summary indicator
information. As additional resources become available, an organization may decide to use automatedtools and workflows to process and use threat information.

Some information sharing challenges apply only to the consumption of threat information:•

Accessing External Information. Organizations need the infrastructure to access external sources
and incorporate the information retrieved from external sources into local decision-making processes.
Information received from external sources has value only to the extent that an organization isequipped to act on the information.

•

Evaluating the Quality of Received Information. Before acting on threat information, an
organization needs to confirm that the information is correct, that the threat is relevant, and that therisks of using or not using the information (i.e., potential impacts of action vs. inaction) are wellunderstood.

Several challenges are only applicable if an organization wants to provide its own information to otherorganizations:•

Complying with Legal and Organizational Requirements. An organization’s executive and legal
teams may restrict the types of information that the organization can provide to others. Such
restrictions may include limits on the types of information and the level of technical detail provided.
These safeguards are appropriate when they address legitimate business, legal, or privacy concerns,
but the imposition of unwarranted or arbitrary restrictions may diminish the utility, availability,
quality, and timeliness of shared information.

•

Limiting Attribution. Organizations may openly participate in information sharing communities, but
still require that their contributions remain anonymous. Unattributed information sharing may allow
an organization to share more information because there is less perceived risk to the organization’s
reputation. The lack of attribution may, however, limit the usefulness of the information because
users may have less confidence in information that originates from an unknown source. If the original
sources of information cannot be identified, organizations may be unable to confirm that information
has been received from multiple independent sources, and thus reduce an organization’s ability tobuild confidence in received information.

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GUIDE TO CYBER THREAT INFORMATION SHARING

Establishing Sharing Relationships

When launching a threat information sharing capability, the following planning and preparation activities
are recommended: 4This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150•

Define the goals and objectives of information sharing (section 3.1).

•

Identify internal sources of threat information (section 3.2).

•

Define the scope of information sharing activities (section 3.3).

•

Establish information sharing rules (section 3.4).

•

Join a sharing community (section 3.5).

•

Plan to provide ongoing support for information sharing activities (section 3.6).

Throughout this process, organizations are encouraged to consult with subject matter experts both insideand outside their organization. Such sources include:•

Experienced cybersecurity personnel,•

Members and operators of established threat information sharing organizations,•

Trusted business associates, supply chain partners, and industry peers, and•Personnel knowledgeable about legal issues, internal business processes, procedures, and systems.

An organization should use the knowledge and experience from these experts to help shape a threat
information sharing capability that supports its mission and operates under its security, privacy,
regulatory, and legal compliance requirements. Due to constantly changing risks, requirements, priorities,
technology, and/or regulations, this process will often be iterative. Organizations should reassess andadjust their information sharing capabilities as needed based on changing circumstances. Such a change
may involve repeating some or all of the planning and preparation activities listed above.
3.1

Define Information Sharing Goals and Objectives

At the outset, an organization should establish goals and objectives that describe the desired outcomes of
threat information sharing in terms of the organization’s business processes and security policies. These
goals and objectives will help guide the organization through the process of scoping its information
sharing efforts, selecting and joining sharing communities, and providing ongoing support for information
sharing activities. Due to technological and/or resource constraints, it may be necessary to prioritize goals
and objectives to ensure that the most important information sharing activities are performed.
3.2

Identify Internal Sources of Cyber Threat Information

A key step in any information sharing effort is to identify potential sources of threat information within an
organization. By conducting an inventory of internal threat information sources, an organization is better
able to identify knowledge gaps. These gaps can be addressed by deploying additional tools and sensors
or by acquiring threat information from external threat information feeds or repositories. In large
4
Although an order for these activities is described, in practice the sequence of these activities can vary, and activities can evenbe performed concurrently. For example, when joining an established sharing organization, it may make sense to address
information sharing rules as part of joining the community.

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organizations, this inventory process is also a means of discovering information that is being collected
and analyzed in business units across the organization that may not be currently shared within theorganization.
The process of identifying threat information sources includes the following steps:

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150•

Identify sensors, tools, data feeds, and repositories that produce threat information, and confirm thatthe information is produced at a frequency, precision, and accuracy to support cybersecurity decisionmaking.

•Identify threat information that is collected and analyzed as part of an organization’s continuous
monitoring strategy.

•

Locate threat information that is collected and stored, but not necessarily analyzed or reviewed on an
ongoing basis. If an organization finds useful threat information that is being underutilized, methodsof integrating this information into its cybersecurity and risk management practices should be
explored.

•

Identify threat information that is suitable for sharing with outside parties and that could help themmore effectively respond to threats.

The owners and operators of threat information sources play an important role in the inventory process
and should be consulted. These personnel understand what information is available and how it is natively
stored; the data export formats that are supported; and the query languages, protocols, and services
available for data retrieval. Some sources may store and publish structured, machine-readable data, whileothers may provide unstructured data with no fixed format (e.g., free text or images). Structured data thatis expressed using open, machine-readable, standard formats can generally be more readily accessed,
searched, and analyzed by a wider range of tools. Thus, the format of the information plays a significant
role in determining the ease and efficiency of information use, analysis, and exchange.
As part of the inventory process, organizations should take note of information gaps that may prevent
realization of the organization’s goals and objectives. By identifying these gaps, an organization is better
able to prioritize investments into new capabilities, and identify opportunities to fill gaps by acquiring
threat information from other, possibly external, sources or through the deployment of additional tools or
sensors.
Table 3-1 describes common sources of cybersecurity-related information and provides examples of data
elements from these sources that may be of interest to security operations personnel.
Table 3-1: Selected Internal Information Sources
SourceExamplesNetwork Data Sources

Router, firewall, Wi-Fi, remote
services (such as remote login or
remote command execution), andDynamic Host Configuration
Protocol (DHCP) server logs

Timestamp
Source and destination IP address
Domain name
TCP/UDP port number
Media Access Control (MAC) address
Hostname
Action (deny/allow)
Status code
Other protocol information

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SourceDiagnostic and monitoring tools(network intrusion detection andprevention system, packet
capture & protocol analysis)

ExamplesTimestamp
IP address, port, and other protocol information
Network flow data
Packet payload
Application-specific information
Type of attack (e.g., SQL injection, buffer overflow)
Targeted vulnerability
Attack status (success/fail/blocked)
Host Data Sources

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Operating system and application
configuration settings, states, andlogs

Bound and established network connection and port
Process and thread
Registry setting
Configuration file entry
Software version and patch level information
Hardware information
User and group
File attribute (e.g., name, hash value, permissions, timestamp, size)
File access
System event (e.g., startup, shutdown, failures)
Command history

Antivirus products

Hostname
IP address
MAC address
Malware name
Malware type (e.g., virus, hacking tool, spyware, remote access)File name
File location (i.e., path)
File hash
Action taken (e.g., quarantine, clean, rename, delete)

Web browsers

Browser history and cache including:•Site visited•
Object downloaded•
Object uploaded•
Browser extension installed or enabled•
Cookies
Other Data Sources

Security Information and EventManagement (SIEM)

Summary reports synthesized from a variety of data sources (e.g., operating
system, application, and network logs)

Email systems

Email messages:
Email header content•
Sender/recipient email address•
Subject line•
Routing information
Attachments
URLs
Embedded graphic

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SourceExamplesThis publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Help desk ticketing systems,
incident management/tracking
system, and people from within
the organization

Analysis reports and observations regarding:•
TTPs•
Campaigns•
Affiliations•
Motives•
Exploit code and tools•
Response and mitigation strategies•
Recommended courses of action
User screen captures (e.g., error messages or dialog boxes)

Forensic toolkits and dynamic
and/or virtual execution
environments

Malware samples
System artifacts (network, file system, memory)

Organizations should update the inventory when new sensors, repositories, or capabilities are deployed orwhen significant changes to a device’s configuration, ownership, or administrative point of contact occur.
3.3

Define the Scope of Information Sharing Activities

Organizations should specify the scope of their information sharing activities by identifying the types of
information available to share, the circumstances under which sharing this information is permitted, andthose with whom the information can and should be shared. Organizations should review theirinformation sharing goals and objectives while scoping information sharing activities to ensure thatpriorities are addressed. When defining these activities, organizations should ensure that the information
sources and capabilities needed to support each activity are available. Organizations should also consider
pursuing sharing activities that will address known information gaps. For example, an organization might
not have an internal malware analysis capability, but it may gain access to malware indicators byparticipating in a sharing community.
The breadth of information sharing activities will vary based on an organization’s resources and abilities.
By choosing a relatively narrow scope, an organization with limited resources can focus on a smaller setof activities that provides the greatest value to the organization and its sharing partners. An organization
may be able to expand the scope as additional capabilities and resources become available. Such anincremental approach may help to ensure that information sharing activities support an organization’s
information sharing goals and objectives, while at the same time fit within available resources.
Organizations with greater resources and advanced capabilities may choose a larger initial scope thatallows for a broader set of activities in support of their goals and objectives.
The degree of automation available to support the sharing and receipt of threat information is a factor toconsider when establishing the scope of sharing activities. Less automated approaches or manualapproaches, which require direct human intervention, may increase human resource costs and limit thebreadth and volume of information that can be processed. The use of automated exchange mechanisms
can help reduce human resource costs, and allow an organization to exchange threat information on alarger scale. Automated threat information sharing concepts are further discussed in section 4.
3.4

Establish Information Sharing Rules

Before sharing threat information, organizations should:•

List the types of threat information that may be shared.

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Describe the conditions and circumstances when sharing is permitted.

•

Identify approved recipients of threat information.

•

Describe any requirements for redacting or sanitizing information to be shared.

•

Specify if source attribution is permitted.

•

Apply information handling designations that describe recipient obligations for protecting
information.

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Sharing rules help control the publication and distribution of threat information, and consequently help toprevent the dissemination of information that, if improperly disclosed, may have adverse consequences
for the organization or its customers or business partners. Information sharing rules should take into
consideration the trustworthiness of the recipient, the sensitivity of the shared information, and thepotential impacts of sharing (or not sharing). For example, an organization may establish rules that limit
the exchange of highly sensitive information to internal individuals or groups, that allow the sharing ofmoderately sensitive information with specific trusted partners, that permit information having a low
sensitivity to be published within a closed sharing community, and that allow for the free exchange of
non-sensitive information within public information sharing forums.
Large organizations that want to share internal threat information across business units may also need toestablish rules governing the exchange of threat information between organizational elements. Business
units within an organization that either collect or process threat information should participate in scoping
what types of threat information will be shared and how that will be done. The steps for establishing
information sharing rules apply to internal sharing of threat information within large organizations.
Multinational corporations need to consider the differences in various nation’s privacy laws and how toaddress handling of classified information, which typically cannot be shared with foreign nationals.
When establishing and reviewing information sharing rules, organizations should request input from theirlegal and privacy officials, information owners, the management team, and other key stakeholders toensure that the sharing rules align with the organization’s documented policies and procedures. Sharing
rules can specified in a variety of ways including, Memoranda of Understanding (MOUs), NonDisclosure Agreements (NDAs), Framework Agreements 5, or other agreements. Organizations areencouraged to proactively establish threat information sharing agreements as part of their ongoingcybersecurity operations rather than attempting to put such agreements into place while under duress inthe midst of an active cyber incident.
An organization’s information sharing rules should be reevaluated on a regular basis. Some of the events
that can trigger reevaluation are:•

Changes to regulatory or legal requirements,•

Updates to organizational policy,•

Introduction of new information sources,•

Risk tolerance changes,

5 An example of such an agreement is the Defense Industrial Base (DIB) Cyber Security/Information Assurance (CS/IA) Program
standardized Framework Agreement [4] which implements the requirements set forth in Title 32 Code of Federal Regulations,
Part 236, Sections 236.4 through 236.6.

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Information ownership changes,•

Changes in the operating/threat environment, and•Organizational mergers and acquisitions.

3.4.1

Information Sensitivity and Privacy

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Many organizations handle information that, by regulation, law, or contractual obligation, requires
protection. This includes PII, CUI, and other sensitive information afforded protection under the
Sarbanes-Oxley Act (SOX), the Payment Card Industry Data Security Standard (PCI DSS), the Health
Information Portability and Accountability Act (HIPAA), the Federal Information Security Modernization
Act of 2014 (FISMA), and the Gramm-Leach-Bliley Act (GLBA) and other legislation, regulations, andguidelines. Organizations should identify and properly protect such information. An organization’s legalteam, privacy officers, auditors, and experts familiar with the various regulatory frameworks should be
consulted when developing procedures for identifying and protecting sensitive information.
From a privacy perspective, one of the key challenges with threat information sharing is the potential fordisclosure of PII 6. Education and awareness activities are critical to ensure that individuals responsible forhandling threat information understand how to recognize and safeguard PII. 7 Internal sharing of
information may result in disclosure of PII to people who, by virtue of their job functions, would not
typically have routine access to such information. For example, a forensic analyst or incident responder
may encounter PII while searching a hard drive for malware indicators, reviewing emails related tosuspected phishing attacks, or inspecting packet captures. The analyst has a legitimate need to review thisinformation to investigate an exploit, develop detection strategies, or develop defensive measures. If theresult of such an analysis is shared with others, steps should be taken to protect the confidentiality of PII.
An organization should have information sharing policies and procedures in place that provide guidance
for the handling of PII. These policies and procedures should include steps for identifying incident datatypes that are likely to contain PII. Policies should describe proper safeguards for managing the privacy
risks associated with sharing such data. A common practice is to focus on the exchange of indicators to
the maximum extent possible. Some indicators, such as file hashes, network port numbers, registry key
values, and other data elements, are largely free of PII. Where PII is identified, however, organizations
should redact fields containing PII that are not relevant to investigating or addressing threats before
sharing. 8 The type and degree of protection applied should be based on the intended use of theinformation, the sensitivity of the information, and the intended recipient.

6 OMB Memorandum 07-16 [5] defines PII as “information which can be used to distinguish or trace an individual’s identity,
such as their name, social security number, biometric records, etc. alone, or when combined with other personal or identifying
information which is linked or linkable to a specific individual, such as date and place of birth, mother’s maiden name, etc.”
OMB Memorandum 10-22 [6] further states that “the definition of PII is not anchored to any single category of information or
technology. Rather, it demands a case-by-case assessment of the specific risk that an individual can be identified. In performing
this assessment, it is important for an agency to recognize that non-PII can become PII whenever additional information is madepublicly available — in any medium and from any source — that, when combined with other available information, could be
used to identify an individual.” NIST SP 800-122 [7] includes a slightly different definition of PII that is focused on the security
objective of confidentiality and not privacy in the broad sense. Definitions of PII established by organizations outside of thefederal government may vary based on the consideration of additional regulatory requirements. The guidance in this document
applies regardless of how organizations define PII.
7 For additional guidance and examples of privacy controls, see NIST SP 800-53 Rev. 4, Appendix J, “Privacy Control Catalog,
Privacy Controls, Enhancements, and Supplemental Guidance” [8].
8 NIST SP 800-122 [7] describes a process called “de-identification” which entails the removal or obfuscation of PII, such thatthe remaining information cannot be used to identify an individual.

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Where practical, organizations are encouraged to use automated methods rather than human-oriented
methods to identify and protect PII. Manual identification, extraction, and obfuscation of PII can be aslow, error-prone, and resource-intensive process. Automated methods may include field-level data
validation using permitted values lists, searching for PII using pattern matching techniques such as
regular expressions, and performing operations that de-identify, mask, and anonymize data containing PII.
The degree of automation that can be achieved will vary based on factors such as the structure,complexity, and sensitivity of the information.

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Organizations should also implement safeguards to protect intellectual property, trade secrets, and otherproprietary information from unauthorized disclosure. The disclosure of such information could result in
financial loss, violate NDAs or other sharing agreements, be cause for legal action, or damage anorganization’s reputation. Organizations should have a plan in place to address the unauthorized or
inadvertent disclosure of CUI. The plan should cover containment, control, and recovery procedures;
breach notification requirements, and post-incident activities such as capturing lessons learned.
Table 3-2 introduces selected types of threat information, provides examples of sensitive data that may bepresent in these types of threat information, and offers general recommendations for handling such data.
Table 3-2: Handling Recommendations for Selected Types of Sensitive Data
Type of Threat
Information
Network
Indicators

Examples of Sensitive Data
Elements 9

Recommendations

Any single network indicator can besensitive, but network indicators in theaggregate are often more sensitive
because they can reveal relationships
between network entities. By studying
these relationships it may be possible
to infer the identity of users, gather
information about the posture ofdevices, perform network
reconnaissance, and characterize thesecurity safeguards and tools that anorganization uses.

Focus on the exchange of network indicatorssuch as destination IP addresses associated withan actor’s command and control infrastructure,malicious URLs/domains, and staging servers.
Before sharing, anonymize or sanitize network
indicators that contain IP or MAC addresses oftarget systems or addresses registered to yourorganization. Also anonymize or sanitize
indicators that may reveal the structure of internal
networks, or ports or protocols that identify
particular products.

9 The PII confidentiality impact level as discussed in NIST SP 800-122 [7] is a useful tool for gauging sensitivity of PII.

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Type of Threat
Information

Examples of Sensitive Data
Elements 9

Recommendations

Packet Capture(PCAP)In addition to the network indicators
previously discussed, unencrypted or
decrypted packets may containauthentication credentials andsensitive organization information,such as PII, CUI or other types ofsensitive information.

PCAP files can be challenging because network
indicators may be present within both the packet
header and the payload. For example, PCAP files
may show protocols (e.g., DHCP, Address
Resolution Protocol (ARP), File Transfer Protocol(FTP), DNS) and applications operating at
multiple layers within the network stack. These
protocols and applications generate network
information that may be captured within PCAP
files and may require sanitization oranonymization to prevent sensitive information
leakage.
Filter PCAP files before sharing by extracting
only those packets that are related to theinvestigation of a specific incident or pattern of
events:•Related to a particular network
conversation (i.e., exchange of
information between specific IP
addresses of interest);•

Occurring during a chosen time period;•

Destined for, or originating from, aspecific port; or•

Use of a particular network protocol.

Redact payload content that contains PII, CUI or
other types of sensitive information that is not
relevant for characterizing the incident or event ofinterest.
When anonymizing or redacting network
information, use a strategy that preserves
enough information to support meaningful
analysis of the resulting PCAP file contents.
Network Flow
Data

Network flow data contains informationsuch as:•Source IP address (i.e., thesender),•Destination IP address (i.e.,
the recipient),•

Port and protocol information,•

Byte counts, and•Timestamps.

If not effectively anonymized, network
flow data may make identification of
specific users possible, provide
insights into user behavior (e.g., websites visited), expose application andservice usage patterns, or reveal
network routing information and data
volumes.

13

Before sharing network flow data, organizations
should consider redacting portions of session
histories using cryptography-based, prefixpreserving, IP address anonymization techniques
to prevent network identification or to conceal
specific fields within the session trace (e.g., timestamps, ports, protocols, or byte counts). To gain
the greatest value from the information, use atool that transforms network flow data without
breaking referential integrity. Network flow
analysis and correlation operations often requirethat IP address replacement and transformation
operations are performed consistently within andsometimes across multiple files. Anonymization
techniques that do not use a consistent
replacement strategy may reduce or eliminate thevalue of sharing this type of information.

NIST SP 800-150

Type of Threat
Information
Phishing EmailSamples

GUIDE TO CYBER THREAT INFORMATION SHARING

Examples of Sensitive Data
Elements 9

Recommendations

Email headers may contain
information such as:

Organizations should anonymize email samples
and remove any sensitive information that is notnecessary for describing an incident or event ofinterest.

•

Mail agent IP addresses,•

Host or domain names, and•Email addresses.

An email message body may also
contain PII, CUI, or other types ofsensitive information.
This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

System,Network, andApplication
Logs

Log files may contain PII, CUI or othertypes of sensitive information. Log
data may reveal IP addresses, ports,
protocols, services, and URLs, as wellas connection strings, logon
credentials, portions of financialtransactions, or other activities
captured in URL parameters.

Organizations should perform IP address,
timestamp, port, and protocol anonymization andremove any sensitive information that is notnecessary for describing an incident or event ofinterest. Before sharing log data, it may also benecessary to sanitize URLs that containidentifying information such as session or user
identifiers. Application logs may require redaction
and anonymizing operations that are specific toparticular application log formats.

MalwareIndicators andSamples

Although organizations are unlikely to
encounter sensitive information in
malware indicators or samples,
sensitive information may be present
depending on how targeted themalware is and what collection
methods were used to gather asample.

Organizations should remove PII, CUI, and othertypes of sensitive information that is notnecessary for describing an incident or event ofinterest.

3.4.2

Sharing Designations

A variety of methods exist to designate handling requirements for shared threat information. Thesedesignations identify unclassified information that may not be suitable for public release and that may
require special handling. A designation applied to threat information can communicate specific handlingrequirements and identify data elements that are considered sensitive and should be redacted prior tosharing. Organizations are encouraged to provide clear handling guidance for any shared threat
information. Likewise, recipients of threat information should observe the handling, attribution,dissemination, and storage requirements expressed in the source organization’s handling guidance.
The Traffic Light Protocol (TLP), depicted in Table 3-3, provides a framework for expressing sharing
designations [9].

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Table 3-3: Traffic Light Protocol, Version 1.0

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Color

When should it be used?

How may it be shared?

TLP:REDNot fordisclosure,restricted toparticipants only.

Sources may use TLP:RED when
information cannot be effectively acted
upon by additional parties, and could leadto impacts on a party's privacy,
reputation, or operations if misused.

TLP:AMBER
Limiteddisclosure,restricted toparticipants’organizations.

Sources may use TLP:AMBER when
information requires support to beeffectively acted upon, yet carries risks to
privacy, reputation, or operations if
shared outside of the organizations
involved.

TLP:GREEN
Limiteddisclosure,restricted to thecommunity.

Sources may use TLP:GREEN when
information is useful for the awareness ofall participating organizations as well aswith peers within the broader community
or sector.

TLP:WHITE
Disclosure is not
limited.

Sources may use TLP:WHITE when
information carries minimal or noforeseeable risk of misuse, in accordancewith applicable rules and procedures for
public release. Subject to standard
copyright rules.

Recipients may not share TLP:RED
information with any parties outside of thespecific exchange, meeting, or conversationin which it was originally disclosed. In thecontext of a meeting, for example, TLP:RED
information is limited to those present at
the meeting. In most circumstances,
TLP:RED should be exchanged verbally or inperson.
Recipients may only share TLP:AMBER
information with members of their own
organization, and with clients or customers
who need to know the information toprotect themselves or prevent further harm.
Sources are at liberty to specify additional
intended limits of the sharing: these must be
adhered to.
Recipients may share TLP:GREEN
information with peers and partnerorganizations within their sector orcommunity, but not via publicly accessible
channels. Information in this category canbe circulated widely within a particularcommunity. TLP:GREEN information may not
be released outside of the community.
TLP:WHITE information may be distributed
without restriction.

The TLP specifies a color-coded set of restrictions that indicate which restrictions apply to a particular
record. In the TLP, red specifies the most restrictive rule, with information sharable only in a particularexchange or meeting, not even within a participant’s own organization. The amber, green, and white color
codes specify successively relaxed restrictions.
The Anti-Phishing Working Group (APWG) has also proposed a schema for expressing sharing
designations [10]. The APWG schema describes an extensible, hierarchical tagging system that can beused to express distribution restrictions on shared information. The tags can be used to indicate withwhom the information may or may not be shared (e.g., recipient only, with affected parties only, no
restrictions) and to express other caveats (e.g., that no attribution is permitted).
For some threat information, collection methods may be considered confidential or proprietary, but theactual indicators observed may be shareable. In such cases, an organization may want to use tear line
reporting, an approach where reports are organized such that information of differing sensitivity is notintermingled (e.g., the indicator information is presented in a separate part of the document than the

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collection methods). Organizing a report in this manner allows an organization to readily produce a reportcontaining only information that designated recipients are authorized to receive.
An organization should carefully choose, or formulate, an approach for expressing sharing designations.
Regardless of how an organization expresses sharing designations, the procedures for applying
designations to threat information should be documented and approved, and the personnel responsible forassigning such designations properly trained.
3.4.3

Cyber Threat Information Sharing and Tracking ProceduresThis publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Over time, an organization’s cybersecurity activities can result in the accumulation of large quantities of
threat information from various sources, both internal and external. Though challenging, tracking of data
sources is important both for protecting information owners and for ensuring that consumingorganizations can meet their legal or regulatory commitments for data protection. Organizations should
also preserve the provenance of data by tracking who provided the information and how the information
was collected, transformed, or processed, information that is important for drawing conclusions fromshared information.
An organization should formulate procedures that allow prompt sharing of threat information while at thesame time satisfying its obligations for protecting potentially sensitive data. The procedures should, to theextent possible, balance the risks of possibly ineffective sharing against the risks of possibly flawedprotection. An organization’s information sharing and tracking procedures should:•

Identify threat information that can be readily shared with trusted parties.

•

Establish processes for reviewing, sanitizing, and protecting threat information that is likely tocontain sensitive information.

•

Develop plan for addressing leakage of sensitive data.

•

Automate the processing and exchange of threat information where possible.

•

Describe how information handling designations are applied, monitored, and enforced.

•

Accommodate non-attributed information exchange, when needed.

•

Track internal and external sources of threat information.

The procedures should describe the roles, responsibilities, and authorities (both scope and duration) of all
stakeholders. The procedures should allow for the effective transfer of authority and flow of shared
information to key decision makers and should enable collaboration with approved external communities
when needed.
3.5

Join a Sharing Community

When evaluating potential sharing partners, an organization should look to sources that complement its
existing threat information resources or that offer actionable information that addresses known gaps in an
organization’s situational awareness. Since sharing communities may focus on the exchange of a specific
type of threat information, an organization may need to participate in multiple information sharing forums
to meet its information sharing objectives.
Threat information can be acquired from public and private sharing communities, government
repositories, across the organization, commercial threat information feeds, and open sources. Sharing
communities often organize around a shared characteristic or interest. The composition of a community

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may be based on geographic region, political boundary, industrial sector, business interest, or threat space(e.g., focused on phishing attacks). Many of these communities have multinational constituencies andglobal reach. Examples of potential sharing partners are ISACs, domestic and foreign Computer
Emergency Readiness Teams (CERTs) or CSIRTs, Information Sharing and Analysis Organizations(ISAOs), DHS Automated Indicator Sharing (AIS) initiative, threat and vulnerability repositories, law
enforcement agencies, product vendors, managed security service providers, internet service providers,
supply chain partners, industry sector peers, business partners, and customers.

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

Some communities are informal, open, self-organizing groups that largely operate through voluntarycooperation. The membership of these communities is often mutable (i.e., no formal fixed membership),sometimes anonymous, and the members may maintain full autonomy with minimal central coordination.
These communities generally operate under basic rules of conduct rather than formal agreements. In such
communities, members publish threat information to the community on a voluntary, ad hoc basis and are
individually responsible for ensuring that the content provided to the community is suitable for sharing.
Organizations wishing to consume information can subscribe to or access various delivery mechanisms
offered by a community such as web services, email or text alerts, and RSS feeds. Such sharing
communities generally make no assertions regarding the quality and accuracy of data provided by theirmembers, and the degree to which the information should be trusted depends on the reputation ofsubmitters (if known).
In contrast, formal sharing communities may define specific membership rules such as:•

Membership fee structures;•

Eligibility requirements for institutions (e.g., must operate within a specific industry sector);•

Eligibility requirements for individuals (e.g., must have enterprise-wide security responsibilities);•

Nomination or sponsorship requirements (i.e., brokered trust);•

Probationary membership period requirements;•

Types of threat information the community provides/accepts;•

Standard delivery mechanisms, formats, and protocols supported by the community; and•Required organizational cybersecurity capabilities.

Formal communities may recruit members by invitation or through sponsorship, and, as such, members
are vetted. Membership rosters in formal communities are generally more stable than those of informal
communities. The exchange of information in a formal community is often governed through service
level agreements (SLAs), NDAs, and other agreements that describe the responsibilities of its members
and participating organizations. Some communities collect an annual membership fee to cover theservices and administrative costs of the community. These fees vary by community and the fee structure
is sometimes tiered, providing for different levels of membership and service.
Before entering into information sharing agreements, an organization should obtain approval from the:•Leadership team that has oversight for information sharing activities and for controlling the resources
necessary to support the organization’s information sharing goals;

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Legal team or those with the authority to enter into commitments; and•Privacy officers and other key stakeholders that have a role in the collection, ingest, storage, analysis,
publication, or protection of threat information.

When choosing a sharing community, consideration should be given to the types of information that areshared within the community, the structure and dynamics of the community, and the cost of entry andsustainment of membership. When evaluating how information is shared within a community, anorganization should consider the following questions:This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150•

Is the threat information shared within the community relevant and does it complement existing threat
information by providing meaningful insights in the context of an organization’s threat environment?

•

Is the threat information exchanged within the community actionable?

•

Does the community have mechanisms in place to accept non-attributed threat information
submissions and the ability to protect a submitter’s identity?

•

Is the threat information timely, reliable, and of known good quality?

•

Are the information exchange formats used by the community compatible with the infrastructure andtools used in an organization?

•

Given the frequency and volume of data sent by a community, does an organization have the capacity
to ingest/analyze/store the information?

In addition to the information shared within a community, consideration should also be given to the
dynamics of the community and its participants, including:•What is the size and composition of the community? (e.g., number of participants, information
producers, and information consumers)•

How active is the community? (e.g., number of submissions or requests per day)•Are community members recruited and vetted? If so, how?

•

What are the technical skills and proficiencies of the community members?

•

What is the community’s governance model?

•

What are the initial and sustained costs of membership?

•

What type of sharing agreement does the community use?

•

Is the sharing agreement well-aligned with an organization’s goals, objectives, and business rules?

•

What are the community’s data retention and disposal policies?

When researching sharing communities, organizations are encouraged to have conversations with current
or former members regarding their experiences as a participant in a community. Such conversation can
provide additional insight and help an organization assess the trustworthiness of a prospective
community.
3.6

Plan to Provide Ongoing Support for Information Sharing Activities

Organizations should develop a support plan that addresses information sharing infrastructure
maintenance and user support. The plan should identify the personnel, funding, infrastructure, andprocesses needed to:18

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Collect and analyze the information from both internal and external sources,•

Acquire and deploy protective measures, and•Acquire and deploy a monitoring and threat detection infrastructure.

Organizations should provide funding for the personnel, infrastructure, and training required for ongoing
operational support for data collection, storage, analysis, and dissemination; for technology refreshment;
and for membership or service fees required for community participation. Although participation in
information sharing activities will require ongoing funding, effective use of threat information may avoid
the potentially much larger costs of successful attacks.

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Participating in Sharing Relationships

An organization’s participation in an information sharing community will typically include some or all of
the following activities:

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Engage in ongoing communication (section 4.1),•

Consume and respond to security alerts (section 4.2),•

Consume and use indicators (section 4.3),•

Organize and store indicators (section 4.4), and•Produce and publish indicators (section 4.5).

The following sections describe these activities in greater detail. Organizations just starting their threat
information sharing efforts should initially choose one or two activities to focus on and should consider
adding activities as their information sharing capability matures. Organizations should understand thatthreat information sharing augments—not replaces—an organization’s fundamental cybersecurity
capabilities, regardless of the maturity of their information sharing practices.
4.1

Engage in Ongoing Communication

Information sharing communities use a variety of communications methods to share threat information
with their members. Most organizations can receive threat information via email lists, text alerts, and web
portals without infrastructure investments specific to information sharing, although the content received
through these delivery channels may need to be manually processed (e.g., “cut and paste” into tools).
Organizations with security tools that support standard data formats can use standards-based data feeds
that enable semi-automated ingest, processing, and use of threat information. Other information sharing
methods, such as conferences and workshops, require dedicated staff and travel. Organizations that
actively produce and share threat information are likely to incur higher communication costs.
Communications may be event-driven (i.e., in response to the actions or behavior of an actor) or periodic,
such as bi-weekly reviews, teleconferences, and annual conferences.
The level of detail, volume, and frequency of messages delivered in human-readable formats varies
widely across information sharing communities. Some communities seek to deliver the most current
threat information with minimal latency. In contrast, some recipients using threat information for trending
and analysis may prefer summary data and may have no need for near real-time delivery of detailed
information. To reduce the number of messages generated, sharing communities sometimes provide theoption of subscribing to digests (i.e., compilations of messages over time intervals) rather than receiving
individual messages.
An organization that has recently joined an information sharing community may require time to integrate
new threat information sources into its existing cybersecurity practices, configure security tools, and train
decision makers on how to interpret and act upon the threat information. During this ramp-up period, anorganization should consult any best practices guidance offered by a community, observe and learn fromthe interactions of more experienced members, and query community support resources (e.g., community
knowledgebase, FAQs, blogs). Community-sponsored training events also provide opportunities for lessmature organizations and inexperienced employees to gain practical insights from skilled practitioners.
Organizations should also establish recruitment and retention processes that reduce personnel turnoverand foster the formation of trusted professional relationships between sharing communities andorganizations. Retention of skilled staff mitigates the loss of institutional knowledge, and preserves
investments in training.

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Ongoing participation in a sharing community is essential for fostering trust, establishing stronger ties toother members, and continuously improving practices. Organizations that actively participate incommunity-sponsored conference calls and face-to-face meetings are better able to establish trust withother members and consequently to effectively collaborate over time.
4.2

Consume and Respond to Security Alerts

An information sharing community may publish security alerts notifying community members of
emerging vulnerabilities, exploits, and other security issues. Fields that commonly appear in security
alerts such as US-CERT alerts, NVD vulnerability advisories, and vendor security bulletins include 10:
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Brief overview/executive summary and detailed description, which would include indicators;•

Platforms affected (e.g., operating system, application, hardware);•Estimated impact (e.g., system crash, data exfiltration, application hijacking) 11;•

Severity rating (e.g., Common Vulnerability Scoring System (CVSS) [11]);•

Mitigation options, including permanent fixes and/or temporary workarounds;•

References for more information; and•Alert metadata (e.g., alert creation and modification dates, acknowledgments).

Upon receipt of a security alert, an organization should determine if the alert came from a trusted, reliable
source. When alerts originate from unknown or untrusted sources, organizations may need to apply
greater scrutiny and/or seek independent confirmation before taking action. If an alert is deemed credible
and it applies to systems, applications, or hardware that the organization owns or operates; theorganization should determine a suitable course of action.
When determining a proper response, an organization should characterize the overall impact of an alert byassessing factors such as the severity of the alert, the number of affected systems within the organization,
the effects an attack might have on the organization’s mission-critical functions, and any operational
impacts related to the deployment of mitigating security controls. This assessment should inform theprioritization and approach for response actions. Response actions include activities such as identifying
and extracting indicators from an alert, using indicators to develop and deploy detection signatures,making configuration changes, applying patches, notifying personnel of threats, and implementing or
enhancing security controls. Extracting indicators is largely a manual process today but there are clear
incentives for automating indicator handling workflows. Manual processing of indicators can be timeconsuming, tedious, error-prone, and slow; automation of the activities allows analysts to focus on theinterpretation of information, rather than routine data manipulations.
4.3

Consume and Use Indicators

The consumption and use of indicators from external feeds is often a multi-step process that includes
some, if not all, of the following activities:

10 Source: US-CERT (https://www.us-cert.gov/).
11 A more extensive list of potential effects is given in the MITRE Common Weakness Enumeration (http://cwe.mitre.org/) andCommon Vulnerabilities and Exposures (http://cve.mitre.org/) listings.

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Validation: verifying the integrity of indicator content and provenance through digital signatures,
cryptographic hashes, or other means.

•

Decryption: transforming encrypted indicator files or data streams back to their original format.

•

Decompression: unpacking compressed indicator files, archive files (e.g., zip, tar), or data streams.

•

Content extraction: parsing indicator files and extracting indicators of interest to an organization. 12•

Prioritization: processing indicators based on relative importance, the perceived value of a data
source, the overall confidence in the data, any operational requirements that specify that data sources
be processed in a particular order, the amount of effort required to transform the data into actionable
information, or other factors.

•

Categorization: reviewing indicator metadata to determine its security designation and handlingrequirements. Sensitive information may require encrypted storage, more stringent access control, or
limitations on distribution.

These activities are typically performed in the order described above, but the order may vary based on
specific operational or security requirements. Where feasible, organizations are encouraged to use
automated techniques to make the indicators available more quickly and reduce manual effort. In cases
where indicators are being informally shared, such as through email, indicator prioritization andcategorization are still important and should be performed by the recipient.
Ideally, indicators are:•Timely. Indicators should be delivered with minimal latency thereby allowing additional time forrecipients to prepare suitable responses. The time criticality of indicators depends on thecharacteristics of the threats, including their severity, speed, and ease of propagation, theinfrastructure being targeted, the TTPs being used, and the capabilities of the actor(s).

•Relevant. Indicators should be applicable to a recipient’s operating environment and address threats
the organization is likely to face. The unnecessary processing of extraneous indicators creates
additional work for analysts and slows down prioritization and categorization actions.

•

Accurate. Indicators should be correct, complete, and unambiguous. Inaccurate or incomplete
information introduces uncertainty and may prevent critical action, stimulate unnecessary action,
result in ineffective responses, or instill a false sense of security. Recipients should be made aware of
any uncertainty or caveats regarding the accuracy of an indicator.

•

Specific. Indicators should provide clear descriptions of observable events that recipients can use todetect threats while minimizing false positives/negatives.

•

Actionable. Indicators should provide enough information and context to allow recipients to develop
a suitable response.

In practice, an indicator may exhibit some, but not all, of these characteristics. For example, a loneindicator may be ambiguous, but when aggregated and analyzed with threat information from other
12 The extraction and handling of content like malware samples should be limited to organizations and individuals who have theknowledge, ability, and infrastructure needed to safely analyze malware. Special handling precautions should be stated andfollowed to prevent inadvertent introduction of malicious code onto production networks.

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sources the indicator is enriched and demonstrates additional value. Also threat information from multiple
sources may vary in precision and accuracy and it is important for users to be able to evaluate theinformation and assign tags that describe the quality or confidence level of the information. The tags areespecially important when an organization needs to resolve discrepancies between threat information
sources. As organizations enrich indicators, any new insights should be shared so that the entire
community may benefit. Organizations may, for example, use externally and internally-generated
indicators to:This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150•

Add or modify rules or signatures used by firewalls, intrusion detection systems, data loss prevention
systems, and/or other security controls to block or alert on activity matching the indicators (forexample, connections involving IP addresses on a blacklist);•

Configure security information and event management solutions or other log management-related
systems to help with analysis of security log data;•

Scan security logs, systems, or other sources of information, using indicators as search keys, toidentify systems that may have already been compromised;•

Find matching records when investigating an incident or potential incident to learn more about athreat, and to help hasten incident response and recovery actions;•

Provide additional information to security operations center analysts;•

Educate staff on threat characteristics; and•Identify threat trends that may suggest changes to security controls are needed.

Typically, an organization’s willingness to use indicators from external sources is strongly affected by thelevel of trust the organization has in the source. Indicators received from a trusted source might be put toimmediate use to detect and respond to a threat. In contrast, indicators originating from an untrusted
source may require independent validation, additional research, or testing before use. Indicator use mightalso be affected by other factors, such as an organization’s tolerance for service disruptions. For someorganizations, security is paramount and occasionally blocking benign activity is considered acceptable.
For other organizations, service availability may be so important that possible malicious activity might
only trigger monitoring.
An organization should carefully consider the characteristics of indicators that it receives and should takea risk-based approach to determining how indicators can be most effectively used. An organization may
find that a specific indicator is useful in some situations but not in others. Ultimately each organizationmust decide how to best use indicators.
4.4

Organize and Store Cyber Threat Information

Organizations may collect indicators from a variety of sources, including open source repositories,
commercial threat feeds, and external partners. Depending on how indicators are being used, there may be
a need to organize them in a knowledgebase. Free-form methods such as wikis can be quite flexible andsuitable for developing working notes and indicator metadata. Structured databases are also useful forstoring, organizing, tracking, querying, and analyzing collections of indicators.

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Information commonly recorded in a knowledgebase includes the following, when known:

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Source of an indicator;•

Rules governing the use or sharing of an indicator;•

Date or time an indicator was collected;•

Length of time that an indicator is still considered valid;•

Whether or not attacks associated with an indicator have targeted specific organizations or sectors;•

Any Common Vulnerability Enumeration (CVE), Common Platform Enumeration (CPE), Common
Weakness Enumeration (CWE), Common Configuration Enumeration (CCE) records associated withan indicator;•

Groups or actors associated with an indicator;•

Aliases of any associated actors;•

TTPs commonly used by an actor;•

Motives or intent of an associated actor;•

Individuals or types of individuals targeted in associated attacks; and•Systems targeted in attacks.

An indicator knowledgebase is an attractive target of attack; therefore effective security practices should
be followed, including implementing access controls, performing regular backups, maintaining operating
system and application software by installing current patches, verifying secure configurations, andfollowing software development best practices for the production of any in-house software used for theknowledgebase.13
Organizations should establish policies and procedures that address the disposition of indicators (andthreat information in general). Policies and procedures should define data retention requirements for short(online) and long (offline) term availability of indicator information. Information handling and retention
requirements may change once threat information is entered into evidence. Evidence acquired during any
incident investigations, for instance, should be collected and preserved using best practices for data
preservation following chain of custody requirements and other laws pertaining to the submission ofevidence. A more detailed treatment of forensic techniques related to chain of custody and preserving
information integrity is available in NIST Special Publication 800-86 [12] and Section 3.3.2 of NIST
Special Publication 800-61 [1].
For indicators that are not needed as evidence, organizations should determine proper retention policies. 14
Although retaining threat information has costs, detailed information may provide historical value as wellas help new sharing community members and partners understand the persistence and evolution ofdifferent actors and attack types. Other considerations, such as financial, legal, contractual, or regulatory
issues, may limit data retention to a fixed period of months or years. Once a retention schedule isidentified, organizations should either archive or destroy the indicators per applicable policies. 15
13 The NIST Software Assurance Metrics and Tool Evaluation (SAMATE) project seeks to develop standard evaluation measuresand methods for software assurance. See http://samate.nist.gov/index.php/SAMATE_Publications.html.
14 Federal agencies are subject to the National Archives and Records Administration (NARA) General Records Schedule as well
as agency-specific retention policies.
15 NIST SP 800-88 [14] provides guidance to assist organizations in making risk-based decisions regarding the sanitization anddisposition of media and information.

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Produce and Publish Indicators

Many organizations only consume indicators. However, some organizations, often those with moreadvanced security capabilities, choose to produce and publish their own indicators. An organization may
benefit substantially by producing threat information. For example, an organization may gain greater
expertise, help other organizations more effectively respond to threats in their environments, and foster
trust with other community members. These effects are important for building and sustaining the flow of
threat information that ultimately benefits a producing organization. A producer of shared threat
information must decide what, if any, metadata should accompany shared information, what data formats
should be used, how sensitive data should be handled, and how information sharing rules should be
updated over time. The following subsections address these issues.
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4.5.1

Indicator Enrichment

Indicators that are produced and published should include metadata that provides context for eachindicator, describes how the indicator is to be used and interpreted and how the indicator relates to otherindicators. Metadata may also include sensitivity designations and provenance information (e.g., what
tool was used to acquire the data, how the data was processed, who collected the data). As indicators are
created, aggregated, or enriched, their sensitivity and classification should be reevaluated. An
aggregation, association, or enrichment process may enable re-identification (e.g., using data mining
techniques) or elevate the sensitivity of the information, thus necessitating additional data handling
restrictions.
The indicator production process should provide a mechanism for publishing indicators, updating
indicators and associated metadata, and retracting submissions that are incorrect or perhaps inadvertently
shared. Any automated mechanisms should be hardened and tested to ensure that they do not become
viable attack vectors for threat actors. Organizations that share indicators should provide a feedback
mechanism that allows sharing partners to submit error reports, suggest improvements, or request
additional information about the indicators. Such feedback plays an important role in the enrichment,
maturation, and quality of the indicators shared within a community.
Some information shared within a community may be marked as “currently under investigation” and may
require that members avoid sharing beyond the collective; such markings may also prohibit members
from performing active information collection (such as retrieving malware samples from a suspect
website, or performing DNS lookups on suspect hostnames) that might tip off a potential actor orotherwise compromise investigative activities. At some point, such information will probably have its
distribution and investigation restrictions downgraded, so a mechanism to change the marking or to add arevised marking such as “downgraded to GREEN as of 12/20/2015” is useful.
4.5.2

Standard Data Formats

The use of standard data formats for the exchange of indicators enhances interoperability and allows
information to be exchanged with greater speed. Unstructured formats (e.g., text documents, email) aresuitable for high-level threat reports and ad hoc exchanges of indicator information and other materials
intended to be read by security personnel rather than machines. For time-critical exchanges of indicators,
however, such as automatically configuring a firewall to block specified communications, the use ofstandard data formats is encouraged because such formats reduce the need for human assistance.
Organizations are encouraged to participate in threat information sharing standards development activities
by sharing use cases, identifying desired features, and providing feedback to standards development

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organizations. 16 Organizations should seek out data formats and exchange protocols that can effectively
support their key threat information sharing use cases, demonstrate a high degree of maturity, broad
adoption, and enable interoperability between a wide range of products and/or organizations.
4.5.3

Protection of Sensitive Data

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The indicators that an organization publishes may be sensitive, so proper safeguards should be used toprevent unauthorized disclosure or modification. Indicator data can be protected using a variety ofmethods, including encrypted network communications, authentication and authorization mechanisms,
and storage in a hardened repository. If a repository is used, an organization should have a written SLA
for the repository that specifies expected availability, security posture requirements, and acceptable use
policies. When producing indicators that may contain sensitive information, proper sharing rules (seesection 3.4) should be followed, and information should be shared only with community members that are
trusted to follow sharing rules and that have agreed to do so.

16 For example, cyber threat information sharing standards development activities have been conducted in both the Organization
for the Advancement of Structured Information Standards (OASIS) and Internet Engineering Task Force (IETF) standards
organizations.

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Appendix A—Cyber Threat Information Sharing Scenarios
This appendix presents some scenarios that describe threat information sharing in real-world applications.
These scenarios seek to show how sharing and coordination can increase the efficiency and effectivenessof an organization’s cybersecurity capabilities. These scenarios represent only a small number of thepossible applications of information sharing and collaboration.
Scenario 1: Nation-State Attacks against a Specific Industry Sector

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A nation-state regularly targets companies in a certain industry sector over several months. The attacks
come in the form of targeted emails that carry malicious attachments containing a software exploit that,upon opening, launches malware on a victim’s system. Systems that are successfully compromised by themalware are then reconfigured by the malware to contact command and control servers and otherinfrastructure operated by the actor to receive additional instructions, download other malware, andperform data exfiltration.
Many companies within this industry sector are members of a formal threat information sharingorganization in which a central forum is used to post information about observed threats. The posts
describe details relevant to detecting and defending against the threat, such as the sender addresses ofphishing emails, samples of malware collected from the attacks, analysis of exploit code used by actors,
the IPs and URLs associated with the actor’s command and control servers, and other infrastructure
involved with attacks.
As soon as one company’s security team identifies a new attack, the information is shared with its peers
within the forum. One of the companies (A) that participates in the forum has advanced malware analysis
capabilities and is able to further characterize the actor and its command and control infrastructure using amalware sample shared via the forum by another company (B). Company A then shares back theinformation gained through its analysis of the malware. Through B’s sharing of the malware sample, thecommunity benefits from the malware analysis capabilities of company A, and is able to quickly andefficiently detect and protect against similar attacks. In this scenario, an attack faced by one company
contributes to another’s defense.
Scenario 2: Campaign Analysis
Cybersecurity analysts from companies in a business sector have been sharing indicators and malware
samples in an online forum over the past few years. Each company performs independent analysis of theattacks and observes consistent patterns over time, with groups of events often having somecommonalities, such as the type of malware used, the DNS domains of command and control channels,
and other technical indicators. These observations lead the analysts to suspect that the attacks are not fully
random, but part of a larger coordinated set of actions.
The forum members participate in technical exchange meetings to share data, insights, and analyses of thedifferent attacks. Through data aggregation and joint analyses, the members can identify activities that arelikely attributable to a common actor or to coordination among actors. This scenario demonstrates how
data fusion and analysis may help reveal collective action and campaigns by a threat actor and identify the
TTPs that are used by specific actors as part of a campaign.
Scenario 3: Distributed Denial of Service Attack against an Industry Sector
A hacktivist group targets a select set of companies for a large-scale distributed denial of service (DDoS)
attack. The group uses a distributed botnet that is loosely coordinated and controlled by members of the27

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group. By analyzing traffic generated by the botnet, one of the companies targeted in the attack is able todetermine that the actors are using a variant of a popular DDoS tool.
The targeted companies are members of an ISAC and use the ISAC’s discussion portal to establish aworking group to coordinate incident response activities. The working group contacts the ISAC’s law
enforcement liaison, who coordinates with federal and international authorities to aid in the investigationand to gain court orders to shut down the actor’s systems.

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The working group contacts various internet service providers (ISPs), and provides information to aid in
identifying abnormal traffic to their network addresses. The ISPs assist both the affected companies andlaw enforcement personnel by helping to identify the upstream and downstream traffic sources,
implementing routing changes, and enforcing data rate limits on these sources. Using network trafficcollected by the ISPs, law enforcement agencies can identify the command and control servers, seize
these assets, and identify some members of the hacktivist group.
After a technical exchange meeting among the targeted companies, several companies decide to enlist theservices of content distribution providers to deploy DDoS-resistant web architectures.
Scenario 4: Financial Conference Phishing Attack
A cyber crime group makes use of a publicly available conference attendee list to target specificindividuals with a wave of phishing emails. The group is able to identify attendees who are members of
the target organization’s corporate accounting team (i.e., individuals who may have the authority toauthorize payments or funds transfers). Using targeted malware, distributed through phishing attacks, thegroup tries to compromise machines and accounts to complete unauthorized electronic payments andfunds transfers to overseas businesses.
One company is able to identify the phishing attack against personnel within its corporate accounting
team and learns, during their investigation, that all the recipients targeted during the attack had attended
the same conference six months earlier. The company’s CSIRT contacts the conference organizers, aswell as representatives from other organizations that attended the conference. The affected organizations
arrange a conference call to share specific information (e.g., email header content, attachments, embedded
URLs) regarding the attacks. Using the shared indicators, other conference attendees review their mailand network traffic logs to identify potentially compromised hosts. These companies agree to ongoingcollaboration and information sharing about future attacks via an informal email list.
Scenario 5: Business Partner Compromise“Company A” and “Company B” are business partners that have established network connectivity
between their organizations to enable the exchange of business information. A cyber crime organization
compromises a server at Company B and uses that access as a stepping stone to launch attacks againstinternal servers at Company A. Operations personnel at Company A notice the unusual activity and notify
their security team. The security team identifies the source of the activity as coming from a Company B
system. As stipulated in their business partner connectivity agreement, Company A notifies Company B
about the anomalous traffic and the companies initiate a joint response to the incident following
established procedures. Company A’s incident response team describes the activity that it sees, allowing
Company B’s team to isolate the compromised server and perform an investigation to identify the sourceof the breach and other possible compromises. Company B’s investigation reveals that the actors
exploited a software flaw in a web-facing application and used it to gain unauthorized access to theserver. The application development team at Company B makes a code change and deploys a patch that28

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fixes the vulnerability, and the security operations team deploys logging and intrusion detection
signatures to identify any similar future attacks.
Because the security teams of the two companies had agreements and processes in place for a joint
response, had pre-established contacts and existing trust relationships, and had already understood eachother’s networks and operations, the companies were able to quickly respond and recover from theincident.
Scenario 6: US-CERT Provides Indicators, Receives Feedback

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The US-CERT receives information, from a variety of independent sources, that servers located in the
U.S. are being used to carry out cyber attacks against other U.S. companies. A specific foreign actor is
known to control the compromised servers. The US-CERT identifies the targeted companies and notesthat most operate within the aviation industry. The US-CERT contacts the security teams of thesecompanies and shares initial threat information, including URLs, malware, and vulnerabilities being
exploited by the actor.
Using the indicators, some of the affected companies are able to detect attacks against their infrastructures
and to take the actions necessary to prevent the attacks from being successful. While investigating
incidents, the affected companies are also able to identify new indicators or provide context regarding theattack to the US-CERT. The US-CERT is able to share these new indicators with other firms afteranonymizing the sources, which leads to a more comprehensive response to the threat.
Scenario 7: A Retailer Fails to ShareA large retailer is subject to a cyber attack by a criminal organization. Millions of credit card numbers andaccount information are stolen during a breach that goes undiscovered for several weeks. The retailer does
not share threat information and relies on its own security and detection capabilities. The retailer’sinternal capabilities prove inadequate in the face of a sophisticated, targeted threat that uses custom
malware.
The breach is discovered by credit card companies investigating a rash of credit card fraud. The credit
card companies determine that the commonality in the credit card fraud was purchases made from thisone retailer. The credit card companies notify both law enforcement and the retailer, and an investigation
is initiated.
The damages are extensive. The retailer notifies its customers of the theft of personal information, butdoes not release details of how the attack was carried out. Consequently, several other retailers are
successfully attacked using the same methods in the weeks following the initial breach. The financial
losses realized by the retailers, customers, and credit card issuers and the reputation loss to the retailers
could have been avoided, at least in part, had the retailers engaged in active sharing of threat information
with one another. The attacker is emboldened by the successful attack and benefits from the delayed
response and lack of a coordination. The attacker benefits financially from the fraudulent activity and canuse these additional resources to expand the scope and sophistication of their operations.

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Appendix B—Glossary
Selected terms used in the publication are defined below.

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Actor

See threat actor.

Alert

A brief, usually human-readable, technical notification regarding
current vulnerabilities, exploits, and other security issues. Also
known as an advisory, bulletin, or vulnerability note.

Continuous Monitoring

Maintaining ongoing awareness of information security,vulnerabilities, and threats to support organizational risk
management decisions. [15]Controlled Unclassified
Information

Information that law, regulation, or government-wide policy requires
to have safeguarding or disseminating controls, excluding
information that is classified under Executive Order 13526,
Classified National Security Information, December 29, 2009, or any
predecessor or successor order, or the Atomic Energy Act of 1954, as
amended. [16]Cyber Threat

See threat.

Indicator

A technical artifact or observable that suggests an attack is imminent
or is currently underway, or that a compromise may have alreadyoccurred.

Information Sharing andAnalysis Organization

An ISAO is any entity or collaboration created or employed bypublic- or private sector organizations, for purposes of gathering andanalyzing critical cyber and related information in order to better
understand security problems and interdependencies related to cybersystems, so as to ensure their availability, integrity, and reliability.
[17]

Metadata

Information describing the characteristics of data including, forexample, structural metadata describing data structures (e.g., data
format, syntax, and semantics) and descriptive metadata describing
data contents (e.g., information security labels). [8]Observable

An event (benign or malicious) on a network or system.

Phishing

Tricking individuals into disclosing sensitive personal information
through deceptive computer-based means. [19]RootkitA set of tools used by an attacker after gaining root-level access to ahost to conceal the attacker’s activities on the host and permit theattacker to maintain root-level access to the host through covertmeans. [18]Sensitive Information

Information, the loss, misuse, or unauthorized access to or
modification of, that could adversely affect the national interest or
the conduct of federal programs, or the privacy to which individuals
are entitled under 5 U.S.C. Section 552a (the Privacy Act), but thathas not been specifically authorized under criteria established by an
Executive Order or an Act of Congress to be kept classified in theinterest of national defense or foreign policy. [18]30

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SensorAn intrusion detection and prevention system component thatmonitors and analyzes network activity and may also perform
prevention actions. [14]Tactics, Techniques, andProcedures (TTPs)

The behavior of an actor. A tactic is the highest-level description ofthis behavior, while techniques give a more detailed description of
behavior in the context of a tactic, and procedures an even lowerlevel, highly detailed description in the context of a technique.

ThreatAny circumstance or event with the potential to adversely impact
organizational operations (including mission, functions, image, or
reputation), organizational assets, individuals, other organizations, or
the Nation through an information system via unauthorized access,destruction, disclosure, or modification of information, and/or denialof service. [2]Threat Actor

An individual or a group posing a threat.

Threat Information

Any information related to a threat that might help an organization
protect itself against a threat or detect the activities of an actor. Major
types of threat information include indicators, TTPs, security alerts,
threat intelligence reports, and tool configurations.

Threat Intelligence

Threat information that has been aggregated, transformed, analyzed,
interpreted, or enriched to provide the necessary context for decisionmaking processes.

Threat Intelligence Report

A prose document that describes TTPs, actors, types of systems andinformation being targeted, and other threat-related information.

Threat Shifting

The response of actors to perceived safeguards and/or
countermeasures (i.e., security controls), in which actors change
some characteristic of their intent/targeting in order to avoid and/or
overcome those safeguards/countermeasures. [2]Tool Configuration

A recommendation for setting up and using tools that support the
automated collection, exchange, processing, analysis, and use of
threat information.

Watering Hole Attack

A security exploit where the attacker infects websites that are
frequently visited by members of the group being attacked, with agoal of infecting a computer used by one of the targeted group when
they visit the infected website.

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Appendix C—Acronyms
Selected acronyms used in the publication are defined below.

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150

ACL
ARP
CCE
CIO
CISO
CPE
CSIRT
CUI
CVE
CVSS
CWE
DDoS
DHCP
DIB
DNS
FISMA
FTP
GLBA
HIPAA
IP
IR
ISAC
ISAO
ISP
IT
ITL
MAC
MOU
NDA
NIST
NVD
OMB
PCAP
PCI DSS
PII
PSIRT
RSS
SIEM
SLA
SOX
SP
SQL
TCP
TLP
TTP
UDP

Access Control List
Address Resolution Protocol
Common Configuration Enumeration
Chief Information Officer
Chief Information Security Officer
Common Platform Enumeration
Computer Security Incident Response Team
Controlled Unclassified Information
Common Vulnerability Enumeration
Common Vulnerability Scoring System
Common Weakness Enumeration
Distributed Denial of Service
Dynamic Host Configuration Protocol
Defense Industrial Base
Domain Name System
Federal Information Security Modernization Act
File Transfer Protocol
Gramm-Leach-Bliley Act
Health Information Portability and Accountability Act
Internet Protocol
Interagency Report or Internal Report
Information Sharing and Analysis Center
Information Sharing and Analysis Organization
Internet Service Provider
Information Technology
Information Technology Laboratory
Media Access Control
Memorandum of Understanding
Non-Disclosure Agreement
National Institute of Standards and Technology
National Vulnerability Database
Office of Management and Budget
Packet Capture
Payment Card Industry Data Security Standard
Personally Identifiable Information
Product Security Incident Response TeamRich Site Summary or Really Simple Syndication
Security Information and Event Management
Service Level Agreement
Sarbanes-Oxley Act
Special Publication
Structured Query Language
Transmission Control Protocol
Traffic Light Protocol
Tactics, Techniques, and Procedures
User Datagram Protocol

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URL
US-CERTGUIDE TO CYBER THREAT INFORMATION SHARING

Uniform Resource Locator
United States Computer Emergency Readiness Team

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Appendix D—References

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-150[1]

NIST SP 800-61, Revision 2, Computer Security Incident Handling Guide, August 2012.
http://dx.doi.org/10.6028/NIST.SP.800-61r2[2]

NIST SP 800-30, Revision 1, Guide for Conducting Risk Assessments, September 2012.
http://dx.doi.org/10.6028/NIST.SP.800-30r1[3]

Executive Order 12968, Access to Classified Information, August 2, 1995.
http://www.gpo.gov/fdsys/pkg/FR-1995-08-07/pdf/95-19654.pdf [accessed 9/30/2016][4]

Defense Industrial Base (DIB) Cyber Security/Information Assurance (CS/IA) Program
standardized Framework Agreement, Federal Register 78 FR 64230, October 22, 2013.
http://www.gpo.gov/fdsys/pkg/FR-2013-10-22/pdf/2013-24256.pdf [accessed 9/30/2016][5]

OMB Memorandum 07-16, Safeguarding Against and Responding to the Breach of PersonallyIdentifiable Information, May 22, 2007.
https://www.whitehouse.gov/sites/default/files/omb/memoranda/fy2007/m07-16.pdf [accessed
9/30/2016][6]

OMB Memorandum 10-22, Guidance for Online Use of Web Measurement and Customization
Technology, June 25, 2010.
https://www.whitehouse.gov/sites/default/files/omb/assets/memoranda_2010/m10-22.pdf[accessed 9/30/2016][7]

NIST SP 800-122, Guide to Protecting the Confidentiality of Personally Identifiable Information(PII), April 2010.
http://dx.doi.org/10.6028/NIST.SP.800-122[8]

NIST SP 800-53, Revision 4, Security and Privacy Controls for Federal Information Systems andOrganizations, April 2013 (updated 01-22-2015). http://dx.doi.org/10.6028/NIST.SP.800-53r4[9]

FIRST, Traffic Light Protocol (TLP): FIRST Standards Definitions and Usage Guidance –Version 1.0, September 2016.
https://www.first.org/_assets/resources/tlp-v1.pdf [accessed 9/30/2016][10]

Anti-Phishing Working Group [Github project site],https://github.com/patcain/ecrisp/tree/master/schemas/apwg [accessed 9/30/2016][11]

NIST IR 7435, The Common Vulnerability Scoring System (CVSS) and Its Applicability to Federal
Agency Systems, August 2007.
http://dx.doi.org/10.6028/NIST.IR.7435[12]

NIST SP 800-86, Guide to Integrating Forensic Techniques into Incident Response, August 2006.
http://dx.doi.org/10.6028/NIST.SP.800-86[13]

NIST SP 800-88 Revision 1, Guidelines for Media Sanitization, December 2014.
http://dx.doi.org/10.6028/NIST.SP.800-88r1[14]

NIST SP 800-94, Guide to Intrusion Detection and Prevention Systems (IDPS) February 2007.
http://dx.doi.org/10.6028/NIST.SP.800-94[15]

NIST SP 800-137, Information Security Continuous Monitoring (ISCM) for Federal Information
Systems and Organizations, September 2011.
http://dx.doi.org/10.6028/NIST.SP.800-137[16]

NIST SP 800-171, Protecting Controlled Unclassified Information in Nonfederal Information
Systems and Organizations, June 2015 (updated 01-14-2016).
http://dx.doi.org/10.6028/NIST.SP.800-171

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[17]

[18]
[19]

GUIDE TO CYBER THREAT INFORMATION SHARINGISAO Standards Organization, Information Sharing and Analysis Organization Standards
Organization Product Outline v0.2, May 2, 2016.
https://www.isao.org/drafts/isao-so-product-outline-v0-2 [accessed 9/30/2016]
NIST IR 7298 Revision 2, Glossary of Key Information Security Terms, May 2013.
http://dx.doi.org/10.6028/NIST.IR.7298r2
NIST SP 800-83 Revision 1, Guide to Malware Incident Prevention and Handling for Desktops
and Laptops, July 2013.
http://dx.doi.org/10.6028/NIST.SP.800-83r1

This publication is available free of charge from: http://dx.doi.org/10.6028/NIST.SP.800-15035